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Topic 2 human Digestive System Learning Objectives 2.2.1 The human digestive system Students should: Know that the digestive system is an example of an organ system in which several organs work together to digest and absorb food. Know that Enzymes: - are biological catalysts that speed up chemical reactions in living organisms - are large proteins - catalyse a specific reaction due to the shape of the active site - are denatured by high temperature and extremes of pH due to changes in the shape of the active site - have an optimum temperature - have an optimum pH. Be able to use the ‘lock and key theory’ as a simplified model to explain enzyme action. Be able to recall the sites of production and the action of amylase, proteases and lipases. Be able to understand simple word equations but no chemical symbol equations are required. Know that Digestive enzymes convert food into small soluble molecules that can be absorbed into the bloodstream. Know that Carbohydrases break down carbohydrates to simple sugars and that Amylase is a carbohydrase which breaks down starch. Know that Proteases break down proteins to amino acids. Know that Lipases break down lipids (fats) to glycerol and fatty acids. Know that the products of digestion are used to build new carbohydrates, lipids and proteins, whilst some carbohydrates are used in respiration. Know that Bile is made in the liver and stored in the gall bladder. Know that Bile is alkaline to neutralise hydrochloric acid from the stomach and emulsifies fat to form small droplets which increases the surface area, both of which increase the rate of fat breakdown by lipase. Be able to carry out rate calculations for different chemical reactions Required practical 4: use quantitative reagents to test for a range of carbohydrates, lipids and proteins, including Benedict’s test for sugars; iodine test for starch; and Biuret reagent for protein. Required practical 5: investigate the effect of pH on the rate of reaction of amylase.